// 忽略模式中的值
fn foo(_:i32, y:i32) {
    println!("y is {}", y);
}
// 如
trait A {
    fn bar(x: i32, y: i32);
}
struct B {
    _a: i32,
}
impl A for B {
    fn bar(_: i32, y:i32) {
        println!("y is {}", y);
    }
}
fn main() {
    <B as A>::bar(1,3);

    foo(1, 2);

    let num = (1, 2, 3, 4, 5);
    match num { (one, _, three, _, _) => {
        println!("{} {}", one, three);
    } }
    // 在变量名字前面添加下划线来忽略名字
    let _x = 5; // 标识忽略这个变量
    println!("_x is {}", _x);
    let _y = 10;

    // let s = Some(String::from("Hello!"));
    // if let Some(_c) = s {
    //     println!("s: {}", _c);
    // }
    // println!("s is {:?}", s);

    let s = Some(String::from("Hello!"));
    if let Some(_) = s {
        println!("s: ");
    }
    println!("s is {:?}", s);
}
